BUILD: mworker: mworker-prog needs time.h for the 'now' variable

It wasn't included and it used to get them through other includes.
diff --git a/src/mworker-prog.c b/src/mworker-prog.c
index 9de94a2..5ecd3df 100644
--- a/src/mworker-prog.c
+++ b/src/mworker-prog.c
@@ -26,6 +26,7 @@
 #include <haproxy/global.h>
 #include <haproxy/mworker.h>
 #include <haproxy/task.h>
+#include <haproxy/time.h>
 
 
 static int use_program = 0; /* do we use the program section ? */